Intracellular microelectrode technique will be used to assess the effect of altered membrane fatty acid composition on the passive and active transport properties of the Neurospora crassa plasma membrane. Specifically, we will be looking for transport aberrations caused by the incorporation into membranes of the branched-chain fatty acid phytanic acid (known to cause Refsum's disease in humans) and by incorporation of unsaturated fatty acids into plasma membrane phospholipids. Utilizing different mutants of N. crassa we will employ the same electrophysiological technique to assess the consequences of altering the phospholipid base ratios on membrane transport processes. We will extend the above studies, which deal with the effect of altered lipid composition on the transport properties of a passive, non-rectifying plasma membrane, to an excitable, nerve cell membrane by using the olfactory nerve of the farfish, lepisosteus osseus. Our initial Garfish experiments will establish the physical state, phospholipid and fatty acid composition of the olfactory nerve. The lipid composition of the olfactory nerve will then be altered by manipulating the environmental temperature and diet of the Garfish. The effect of altered lipid composition on excitable membrane parmeters (action potential conduction velocity, refractory period, duration, and sensitivity to different ions) will be determined by extracellular electrophysiological technique.